1. Field of Invention
The present invention relates to a braking method for a single-phase motor and, in particular, to a braking method using a three-phase motor driving IC to drive a single-phase DC brushless motor.
2. Related Art
DC servomotors have superior stability and the relation between the input and output is almost linear, which renders a good controllability; they are therefore widely used in places that require high precision controls. However, the conventional DC motor has a brush and redirector that are subject to erosion. This defect makes the reliability and maintenance of the conventional DC motor worse than other motors. The brushless motor is to replace the rectifier (brush and redirector) of the conventional DC motor with an electronic means so that it is free from the erosion of the brush and redirector and maintenance. Because there is no brush in the structure, it will not generate mechanical and electronic noises in principle. Therefore, such motors have superior properties.
According to the wiring method on the stator, the DC brushless motor can be classified into single-phase type, double-phase ones, three-phase types, five-phase ones, etc. In particular, the three-phase DC brushless motors are more common. Compared with the three-phase DC brushless motor, the single-phase DC brushless motor has the advantages of easy assembly and high yield. Therefore, taking into account the production cost, the single-phase DC brushless motors are more competitive than the three-phase DC brushless motors. Since three-phase motor driving means is still the main stream on the current market and the single-phase motor driving IC is still under development, thus the three-phase motor driving IC has the advantages of mass production and low prices in the motor driving IC industry. If the three-phase motor driving IC can be used to drive the single-phase DC brushless motor, advantages of both of them can be combined to have more competitive power. The time schedule delay in production development due to fewer single-phase motor driving IC manufacturers can be avoided.
Currently, the Opto-Electronics & Systems Laboratories in Industrial Technology Research Institute has successfully applied three-phase motor driving ICs to drive single-phase DC brushless motor. However, the method disturbs the determination of the rotation direction of the main axis motor in the three-phase motor driving IC and results in reverse rotation when the motor braking action stops.